PyQt5 无法重绘 QLabel 的文本

Question

我正在尝试更新 QLabel 以反映日志更改，但它不会重新绘制。 我尝试了多种方法都没有成功，代码中仍然列出了一些。 log_text Label 的值发生变化，它被打印到终端，但从不打印到 GUI。 （灰色区域绑定function改文字）

import sys
from PyQt5 import QtGui, QtCore, QtWidgets
from PyQt5.QtGui import QPainter
from PyQt5.QtCore import QSize
from PyQt5.QtWidgets import (QApplication, QMainWindow, QWidget, QHBoxLayout, QVBoxLayout, QDesktopWidget,
                             QLabel, QAbstractButton, QStackedWidget, QFrame, QTableWidget,)

class MainWindow(QMainWindow):
    def __init__(self):
        super(MainWindow, self).__init__()

        self.center()

        self.setGeometry(500, 200, 1400, 800)

        layout1 = QHBoxLayout()
        layout2 = QVBoxLayout()
        layout3 = QVBoxLayout()
        layouts = QHBoxLayout()

        layout1.setSpacing(0)
        layout2.setSpacing(0)
        layout3.setSpacing(0)
        layouts.setSpacing(0)

        layout1.setContentsMargins(0, 0, 0, 0)
        layout2.setContentsMargins(0, 0, 0, 0)
        layout3.setContentsMargins(0, 0, 0, 0)
        layouts.setContentsMargins(0, 0, 0, 0)
        self.setContentsMargins(0, 0, 0, 0)

        widget = QWidget()
        widget.setLayout(layout1)
        self.setCentralWidget(widget)

        self.setWindowFlags(QtCore.Qt.FramelessWindowHint)

        self.frameR = QFrame()
        self.frameR.setFrameShape(QFrame.StyledPanel)
        self.frameR.setStyleSheet("background-color: rgb(27, 29, 35); border: 0px solid black")
        self.frameR.setFixedWidth(71)
        self.frameR.setFixedHeight(71)
        layout2.addWidget(self.frameR)

        resize_layout = QVBoxLayout()
        self.frameR.setLayout(resize_layout)

        button5 = PicButtonF(QtGui.QPixmap("validationN.png"), QtGui.QPixmap("validationH.png"),
                             QtGui.QPixmap("validationC.png"))
        button5.clicked.connect(self.widget4)
        layout2.addWidget(button5)

        spacer_m = QFrame()
        spacer_m.setFrameShape(QFrame.StyledPanel)
        spacer_m.setStyleSheet("background-color: rgb(27, 29, 35); border: 0px solid black")
        spacer_m.setFixedWidth(71)
        layout2.addWidget(spacer_m)

        layout1.addLayout(layout2)

        label_title = QLabel("  PG - Programme De Gestion")
        label_title.setStyleSheet('background-color: rgb(37, 39, 44); color: white')
        layouts.addWidget(label_title)

        spacer_m = QFrame()
        spacer_m.setFrameShape(QFrame.StyledPanel)
        spacer_m.setStyleSheet("background-color: rgb(37, 39, 44); border: 0px solid black")
        spacer_m.setFixedHeight(45)
        layouts.addWidget(spacer_m)

        top3 = PicButtonF(QtGui.QPixmap("closeN.png"), QtGui.QPixmap("closeH.png"),
                          QtGui.QPixmap("closeH.png"))
        top3.clicked.connect(self.closeapp)
        top3.setFixedWidth(45)
        top3.setFixedHeight(45)
        layouts.addWidget(top3)

        layout3.addLayout(layouts)

        self.frameS = QFrame()
        self.frameS.setFrameShape(QFrame.StyledPanel)
        self.frameS.setStyleSheet("background-color: rgb(38, 41, 50); border: 0px solid black")
        self.frameS.setFixedHeight(24)
        layout3.addWidget(self.frameS)

        self.layoutS = QHBoxLayout()
        self.layoutS.setSpacing(0)
        self.layoutS.setContentsMargins(5, 5, 5, 5)
        self.frameS.setLayout(self.layoutS)

        self.log_text = QtWidgets.QLabel('Text That Must Change')
        self.log_text.setStyleSheet('color: white')
        self.layoutS.addWidget(self.log_text)

        self.stackedWidget = QStackedWidget()
        self.stackedWidget.addWidget(Validation())

        self.frameC = QFrame()
        self.layoutC = QHBoxLayout()
        self.frameC.setLayout(self.layoutC)
        self.layoutC.setSpacing(0)
        self.layoutC.setContentsMargins(0, 0, 0, 0)
        self.layoutC.addWidget(self.stackedWidget)
        layout3.addWidget(self.frameC)

        frame5 = QFrame()
        frame5.setFrameShape(QFrame.StyledPanel)
        frame5.setStyleSheet("background-color: rgb(37, 39, 44); border: 0px solid black")
        frame5.setFixedHeight(25)
        layout3.addWidget(frame5)

        credit_layout = QHBoxLayout()
        frame5.setLayout(credit_layout)

        layout1.addLayout(layout3)

        self.oldPos = self.pos()

    def logging(self, text):
        print(str('Testing - Text Passed Through Function: ') + str(text))
        print(str('Testing - Text Currently Before Function: ') + str(self.log_text.text()))
        self.log_text.setText(str('New Text From Logging Function'))
        self.log_text.hide()
        self.log_text.show()
        self.log_text.repaint()
        self.log_text.update()
        QtWidgets.qApp.processEvents()
        print(str('Testing - Text Set After Function: ') + str(self.log_text.text()))

    def widget4(self):
        self.stackedWidget.setCurrentIndex(4)

    def center(self):
        qr = self.frameGeometry()
        cp = QDesktopWidget().availableGeometry().center()
        qr.moveCenter(cp)
        self.move(qr.topLeft())

    def closeapp(self):
            self.close()

class Validation(QWidget):
    def __init__(self):
        super().__init__()

        self.header = ['CLIENT', 'TYPE']

        header_count = len(self.header)

        self.tableWidget = QTableWidget()
        self.tableWidget.setColumnCount(header_count)
        self.tableWidget.setRowCount(40)
        self.tableWidget.setHorizontalHeaderLabels(self.header)

        layout_tw = QVBoxLayout()
        layout_th = QHBoxLayout()

        frame1 = QFrame()
        frame1.setFrameShape(QFrame.StyledPanel)
        frame1.setStyleSheet("background-color: rgb(144, 149, 160); border: 0px solid black")
        frame1.setFixedHeight(50)
        frame1.setFixedWidth(122)

        frame1l = QHBoxLayout()
        frame1l.setSpacing(0)
        frame1l.setContentsMargins(5, 5, 5, 5)
        frame1.setLayout(frame1l)

        frame1b = PicButtonF(QtGui.QPixmap("query_all.png"), QtGui.QPixmap("query_all.png"),
                             QtGui.QPixmap("query_all.png"))
        frame1b.clicked.connect(self.validation_query)
        frame1l.addWidget(frame1b)

        frame_fill = QFrame()
        frame_fill.setFrameShape(QFrame.StyledPanel)
        frame_fill.setStyleSheet("background-color: rgb(44, 49, 60); border: 0px solid black")
        frame_fill.setFixedHeight(50)

        layout_th.addWidget(frame1)
        layout_th.addWidget(frame_fill)
        layout_tw.addLayout(layout_th)
        layout_tw.addWidget(self.tableWidget)

        layout_tw.setSpacing(0)
        layout_tw.setContentsMargins(0, 0, 0, 0)

        self.setLayout(layout_tw)

    def validation_query(self):
        MainWindow().logging('New Text From The Query Function')

class PicButtonF(QAbstractButton):
    def __init__(self, pixmap, pixmap_hover, pixmap_pressed, parent=None):
        super(PicButtonF, self).__init__(parent)
        self.pixmap = pixmap
        self.pixmap_hover = pixmap_hover
        self.pixmap_pressed = pixmap_pressed

    def paintEvent(self, event):
        pix = self.pixmap_hover if self.underMouse() else self.pixmap
        if self.isDown():
            pix = self.pixmap_pressed

        painter = QPainter(self)
        painter.drawPixmap(event.rect(), pix)

    def enterEvent(self, event):
        self.update()

    def leaveEvent(self, event):
        self.update()

    def sizeHint(self):
        return QSize(71, 71)

class PicButton(QAbstractButton):
    def __init__(self, pixmap, parent=None):
        super(PicButton, self).__init__(parent)
        self.pixmap = pixmap

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.drawPixmap(event.rect(), self.pixmap)

    def sizeHint(self):
        return self.pixmap.size()

def main():
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

Answer 1

您不会更改现有 window 的 label，而是每次都创建一个新的 window：

    def validation_query(self):
        MainWindow().logging('New Text From The Query Function')

该行创建一个MainWindow的新实例并调用该实例的logging function，然后立即删除新实例（收集垃圾），因为没有创建对它的引用。 即使创建了引用（本地或作为实例属性），这显然不是正确的方法。

要正确更改现有window 的 label，您应该使用自定义信号并将其连接到validation_query function。 为此，您也不能只将小部件添加到堆叠布局中，因为您需要参考来连接新信号。

class MainWindow(QMainWindow):
    def __init__(self):
        # ...
        validator = Validation()
        self.stackedWidget.addWidget(validator)
        validator.validateResult.connect(self.logging)
        # ...
 
class Validation(QWidget):
    validateResult = QtCore.pyqtSignal(str)
    # ...
    def validation_query(self):
        self.validateResult.emit('New Text From The Query Function')

我建议您阅读有关类和实例的更多信息。